


Third Wheel

by moviefan



Category: It's Always Sunny in Philadelphia
Genre: Fluff and Smut, Frottage, M/M, Other
Language: English
Status: Completed
Published: 2018-08-21
Updated: 2018-08-21
Packaged: 2019-06-30 17:35:15
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,417
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15756513
Author URL: https://archiveofourown.org/users/moviefan/pseuds/moviefan
Summary: Dennis is recently back from North Dakota and is upset about Mac and Rex's sudden closeness.





	Third Wheel

**Author's Note:**

> I got the idea for this fic earlier this month. I haven't written any fanfic in two years, so I wanted to start writing and see where this went. Hope you enjoy :)

Dennis walks into their apartment and is totally shocked. For as long as he’s known Mac, he’s never unexpectedly walked in on Mac with someone before. Ever since Dennis got back from North Dakota a week ago, he is not happy about whatever is going on between Mac and Rex. It’s annoying enough with Rex hanging out at the apartment so much, but now Dennis has to walk in and get a sight he can never un-see: Rex lying back on the couch with his eyes glazed over, his shirt off (why does he always have his shirt off?), his jeans and boxers down with Mac kneeling between his legs blowing him (why does it annoy Dennis that Mac looked so into it?). Rex startles as soon as he notices Dennis come in.

“Oh, sorry Dennis, we thought you’d be back later” he says as he grabs a cushion to cover himself and hurriedly pulls his jeans back up.

Mac just looks annoyed. “Dude, you said you were coming back in an hour”.

“Okay, well I was a little early. I picked up the movies for tonight”. “Actually, Rex has Netflix and said that we could use his account. Let’s look for something on there tonight”. Dennis forces a smile and manages to get out an “Okay”. Mac looks a bit wary as Dennis walks past them to go into his room.

Later that night, the three of them are sitting on the couch together. Mac and Rex are sitting close together and Dennis is sitting as far to the end of the couch as he can get. Rex picked the new Jason Statham movie. While Dennis is getting bored by the movie, his mind drifts and an intriguing idea starts to form.

“Uh, so how long has this been going on for?” Dennis asks, gesturing between Mac and Rex.

“It’s been a few weeks”, Rex answers.

“Oh yeah, it’s still pretty new then. I guess you’re not at that stage yet where things are starting to get a bit boring in the bedroom”, Dennis replies.

“What are you getting at, bro?” Mac asks, raising an eyebrow.

Dennis inches a bit closer to them. “Well, Mac, as you know, I’ve always been a very exploratory person, sexually. But surprisingly, there’s one thing that’s always been missing. One thing I haven’t done. I’ve…never had a threesome” Dennis looks a bit embarrassed as he says that.

Rex turns to Mac and they talk quietly amongst themselves. After a few minutes, they both turn towards Dennis.

“So, what do you say?” Dennis asks.

“Okay”, Mac says and nods.

“I’m down” Rex says.

“Uh, not yet you’re not, so…” Dennis trails off, whistles and gestures to his own crotch.

“Well, how about we start with kissing first” Rex says, laughing.

The three of them are sitting on Mac’s bed in his room. Dennis will probably kick himself later for not suggesting his own bedroom, but right now he oddly doesn’t want to immortalize this with a tape. Rex turns towards Mac and gently kisses him. Then he turns towards Dennis and does the same. Dennis has never really been one for kissing. The kiss isn’t bad, but he’d rather just get things moving. Shirts and pants all come off, almost as a formality. It feels oddly dispassionate for something that Dennis has expected to be so hot. Mac lays down and pulls Rex on top of him, kissing him. Dennis inches closer to them and runs his hands along Rex’s back. Rex starts kissing Dennis while he runs his hands over Dennis’s body. Mac is just watching. Every once in a while, Rex asks Dennis, “Is this okay?” and it annoys him. Nothing about this is how he imagined. Why is Mac hardly even engaged?. Rex starts stroking Dennis through his briefs and Dennis lets out a moan. It had been an embarrassingly long time since he’d had sex. Rex kneels down on the floor. Dennis lets Rex pull down his briefs and he can feel Rex’s hot breath against his cock. Dennis feels his cock twitching in anticipation, but he looks over at Mac. Mac studying him with his stupid deep brown eyes. Almost absentmindedly palming himself through his boxers with a curious, almost sad expression. This should be Dennis’s dream come true, yet he feels that this is all wrong. Rex notices Dennis’s hard-to-read expression and gets up from the floor.

“Yeah, I don’t think this is working. I kind of feel like I’m in the way here. Mac, I’m sorry, but I think I’m going to leave”. Rex starts pulling his clothes back on. “I think you two need to sort some stuff out, and you haven’t done it because I’ve been around so much. I’ll see you, Mac”. Rex says, gently putting a hand on Mac’s shoulder before leaving the bedroom.

As soon as Mac and Dennis hear the apartment door close, an uncomfortable silence settles in between them. Dennis suddenly remembers he’s naked and pulls his briefs back up. He hopes they can both ignore his hard-on.

“So…that was a bust, huh?” Dennis asks awkwardly.

“I thought you were never coming back” Mac says quietly. “I thought you were going to be in North Dakota forever, and it was so hard for a while. Then I started hanging out with Rex and then we started banging and he was fun. He got me working out and going to the gym with him, and I could forget about you for a bit”. Mac starts to grow a bit angry “Then you just walk back into the apartment last week like nothing changed. Into _our_ apartment that I refurnished, which you didn’t seem to care about at the time. Why did you even come back?”

After a few seconds, Dennis speaks “I missed you. I missed the gang too, but I _really_ missed you. Before I left, I realized something and it scared me. I just wanted to get away and not think about it.

Dennis places his hand on Mac’s.

“I think you’re going to have to tell me” says Mac.

Dennis leans over and kisses Mac gently. He is relieved to find Mac kissing him back. They pull apart after a minute.

“I love you” Dennis says.

“I love you too, you dumbass”, Mac says before kissing him again. Dennis feels a pressure finally start to release, thinking of all the times where they almost kissed, all that time together, and he lets it go.

They start kissing passionately, their hands roaming everywhere. Dennis lays down on the bed and pulls Mac on top of him. Mac tweaks and pinches Dennis’s nipples, making Dennis gasp in pleasure. Dennis starts to grind against Mac until Mac stops them long enough to pull off his boxers. Dennis pulls down his briefs and feels Mac’s weight settle on top of him. Dennis will never get tired of this wonderful skin-to-skin feeling. They kiss lazily for a little while, content. Then Mac lays down and Dennis straddles him. Dennis lines up both their cocks with his hand and starts to stroke slowly. This only lasts a minute before Mac impatiently bats away Dennis’s hand, licks a stripe up his own hand and starts to stroke them both a bit faster. It’s very clear they’re both not going to last long, but Dennis doesn’t care. Dennis hears Mac panting while he has one hand wrapped around their cocks and the other is gripping Dennis’s ass. Dennis bends down so he can kiss Mac, holding his face in his hands and trying to put all the feelings he’s had for Mac for so long into the kiss. Dennis grinds himself against Mac for exactly two seconds and then Mac comes with a low groan. Dennis follows soon after. Watching Mac shudder and moan and knowing it’s because of him is probably the hottest thing Dennis has ever seen. Dennis rolls off of Mac as they catch their breaths. Dennis knows they should probably clean up, but he doesn’t want to move right now. He looks over at Mac, cuddling against him with the sweetest tired expression on his face. He doesn’t care how short this was. One day soon, they’ll take their time, Dennis trying to make Mac come as many times and in as many different ways as possible, but not right now. Dennis settles against Mac, gently kissing his cheek before they both drift into a satisfied sleep.


End file.
